Glass bottles, (quart bottles?) nearly similar to our wine-bottles in color and measure, though in shape resembling the wide-mouthed bottles used in preserving fruit, may be seen in the British Museum, and are found in abundance in other European cabinets. the more elaborate processes of glass-making. There are many striking examples of this proficiency in the new Egyptian room at the British Museum. But we will take the single instance of the tablet of stained glass found at Thebes, and of which Rosellini gives the illustration to which been stated, is tasteful. It consists of a quadruple star, with a rose in the centre, and with foliage on the angles. Blue, yellow, red, and green colors are introduced, and they are struck through the body of the glass. In order to produce this effect of glass-staining, oxides of cobalt, or of calcined copper and zinc, must have been used for blue, oxide of silver for yellow, and oxide of copper for green. The ruby color of the rose, that color of which till lately we had lost the art of imparting, must have been given (as well as the rich purple hue of some of the fictitious gems) by the oxide of gold. This proficiency may appear extraordinary; but indeed, the richly-painted walls of the temples, palaces, and tombs, where the unmatched colors remain as fresh as when first laid on, show not only a perfect proficiency with the mineral pigments, but a perfect use of the metallic oxides in their composition. A remarkable fact connected with the manufac-reference has been made. The design, as has ture of ancient Thebes 4,000 years ago, shows the traditional tenacity of ancient custom. It is well known that the oil-jars of the Levant are precisely similar to those which appear in the illustrations of Rosellini. So the Egyptian earthen amphora, without feet, adopted afterwards for strong wines by the bon vivants of Rome, retain their original shape and purpose among the Tuscan farmers. With reference to glass bottles, there are two classes used at the present day of equally ancient origin these are the Florentine oil-flasks, holding about three quarters of a pint, and the turpentine carboys, as they are called, holding four or five gallons, from Cyprus and the adjoining shores of the Levant. Both are protected by matting, the first of a fine, the second of a coarser nature. Both are seen, with slight alterations, in the illustrations of Rosellini. Sir G. Wilkinson thinks that glass lanterns were used by pickets of soldiers, and gives a specimen of a group of Egyptian sentinels carrying a lantern on a curved pole. It is not improbable that an hieroglyphic on the Rosetta stones, translated manifestation, resembling a magic lantern with a handle, from which rays of light are issuing, may be something of the kind. That the glass-manufacturers made magnifying lenses is clear from Plutarch, (de facie luna,) Diodorus, and Ptolemy, the astronomer, and is proved by the extant cameos, which could only be cut by the aid of a microscope. But reverting to the subject of lanterns, it is probable, though it cannot be gathered from Pliny, that the lamps employed for yearly illumination at the Saite festival-a custom transmitted from remote ages to modern China-may have been of glass. The Egyptians, in the time of the eighteenth dynasty, appear to have used colored lanterns, like the modern Chinese, on the latter as well as ordinary occasions. Indeed, the modern people of Cairo use colored lanterns of striped gauze strained over a wire frame, after the Chinese fashion. But they are cylindrical and less florid and various in their decoration. The singularity is, that in the illustrations of Rosellini precisely similar cylindrical lanterns of colored gauze are seen in the hands of the running footmen and attendants on the grandees of ancient Thebes, when in the act of lighting their masters home from their evening banquets or fêtes champetres. It is as easy as invidious to ascribe these applications to unintelligent accident or experiment, rather than to high proficiency in chemistry. Evidences, drawn from all the other arts and trades, prove that the ancient Egyptians, in the earliest times, were skilful chemists; and why should we deprive the land of Cham, Chemosh, and Chemonis, from which the name and art of chemistry—as well as alchemy, its foster-parent -was derived, of the just tribute due to its original study, discoveries, and inventions? Quid feret Illiæ Mavortisque puer, si taciturnitas Obstaret meritis, invida Romuli? Note.-Winckelman, on the Arts of the Ancients, has some observations on the ancient manufacture of glass, which may be conveniently added. Pliny attributes the discovery of glass to some Phænician mariners, who, having kindled a fire on the beach for the purpose of cooking, placed their utensils on blocks of nitre. The fire melted the nitre and the sand, and produced a vitrified substance, which improvement converted into pure glass. The Tombs of Thebes demonstrate that 4,000 years ago the manufacture of glass was well known to the Egyptians. The frescoes exhibit glass-blowers forming bottles and vials of green glass. The specimens of Egyptian vials in In conclusion, it may be remarked as a singular the British Museum are by no means inelegant; circumstance, and which applies as well to other they have long necks bulging towards the bottom, manufactures, (such as the potteries, metal foun- which, when filled with any liquid, would be deries, the tanners, the turners, the dyers, and much less easily subverted than the vials in comthe hand-loom weavers,) that the initial process mon use amongst us. Pocket-bottles, cased in of glass-making retains its primitive simplicity, leather, such as are used in sporting, for containNow, as 4,000 years ago, the blow-pipe, shod ing spirits or liqueurs, are amongst the curious with iron and heated red-hot, is inserted into the relics of the Theban glass manufacture. It is melted glass. In the ancient manufactories, work-clear, from specimens that are left, that the anmen are employed in bringing the "frit" in baskets, for the purpose of vitrification. There can scarcely be a doubt that this frit is a combination, as in Venetian glass-making derived from Egypt, of kali, from the ashes of salsola communis, or kelp, and a particular kind of sand. But this paper ought not to conclude without some more distinct reference to the chemical knowledge displayed in cient Egyptians knew how to make casts in vitrified materials, and to counterfeit in glass the amethyst and the emerald, with a degree of success unequalled in any country. Nor were they unpractised in the ingenious process by which the representation of a bird or flower may appear to be imprisoned within a piece of glass, so as to form part of its own substance. It appears that such public utility. The vast mass of persons who are now deeply interested in all that belongs to rapid locomotion may have an opportunity of judging for themselves how far the plan proposed is likely to be serviceable: for ourselves, we entertain but one opinion, which is, that it should be urged upon the consideration of all those whose business it is to carry out the gigantic schemes new in agitation. they constructed the device from filaments of colored glass, in the first instance; it was then covered with transparent laminæ of glass, and all were fused together with so much skill that no joinings in any part of the work can even now be detected by the most powerful magnifier. In these specimens the colored device appears as perfect on one side as the other. Figures of birds were thus composed; and if cut through at intervals, each portion so divided contained in "In no subject is an active, energetic, and comitself a perfect copy of the bird. The celebrated mercial people more deeply interested than in the Portland vase was long supposed to be a real sar- means for safe and expeditious intercommunicadonyx; but it is now known to be formed of tion; and, as we have long maintained a high layers of purple-colored glass united by fusion. preeminence among the civilized nations of the By similar superfusion, the glass pieces used in earth for our zeal, enterprize, and commerce, we the mosaics on the vaults of the domes at Venice can only expect to secure these honorable dishave been enabled to preserve unimpaired their tinctions by affording every possible encourageoriginal coloring and gilding. A small diamond ment to those inventions and discoveries which of the glass mosaic was gilded in the usual way, have a tendency to bring the arts and sciences to and then thinly coated with the vitrified material the highest degree of culture and practical utility. while in a state of fusion. This was an Egyptian The truth of this statement has been admitted; art. The gold color and device appear incor- and yet a strange but most decided opposition has porated with and struck through the body of the been raised to almost every remarkable invention glass, so as to appear the same on both sides. that has been introduced during the last fifty An Egyptian sarcophagus of granite may be occa- years. The proposed locomotive steam-carsionally seen cased over in the same manner, in riage was most violently opposed by the devout order to preserve unimpaired the sculptures and lovers of stage-coach travelling. The olden times legends engraved upon the stone. To the eye of and the olden ways were so much admired, that an ordinary observer, several necklaces, scarabæi, any innovations on the olden practices were brooches, and small ornamental figures in the dreaded with a terror-a little less than that felt cases of the new Egyptian Room would appear at an approaching earthquake. That the whole composed of precious stones. They are, in fact, host of interested parties should be opposed to a at least the great majority of them, composed of new and improved mode or travelling was no more glass throughout the whole substance, or of mate- than might be expected, because the doctrine of rials covered with a glass coating. The tasteful vested rights, as maintained and practically carried colored networks of glass bugles, with which the out in this country, had ever been a mighty barwrappers of mummies were decorated, were made rier to all social and moral improvements. But of the same materials, and are remarkable as that parties, who had no such rights to be jeopbeing identical with similar ornaments made into ardized or damaged, should be opposed, must be a bracelets, headbands, and waistbands, by fair dilet-matter of surprise to every reflecting mind; for tantis at the present day. With reference to the larger examples of vitreous superfusion to which reference has been made, a sarcophagus of this description was found by Belzoni in the Tombs of the Kings. The historical assertion is well known, and has frequently provoked commentary, that the body of Alexander, cased in gold, was buried at Alexandria, in a coffin composed entirely of glass. If the record be true, it is probable that the body so inclosed in glass was, for protection sake, reïnclosed within a granite or other more durable sarcophagus. From the Polytechnic Review. ON ATMOSPHERIC RAILWAYS. WE directed the attention of our readers, some short time since, to the probable establishment of atmospheric railways upon many of the great lines of this kingdom: we likewise announced our intention of devoting some space to the consideration of Mr. Pilbrow's invention: this task we have been spared, by the kind permission of Dr. Hewlett to transfer to our columns his admirable paper on the subject, which, when read before the Society of Arts, deservedly obtained the warmest approbation. It explains, in so simple, easy, and intelligible a form, all the leading points, that no language of ours could render it more available to those who feel anxious to know what are the views entertained by the original proprietors of the patent, and those who are about to embark their capital in carrying out a scheme which promises to be of not a few, both in Bristol and Birmingham, were to be found, who, on hearing of the respective railways proposing to accomplish twenty miles an hour, said, with much complacency-Let others venture their necks who please; but as for me I am quite contented to travel at the rate of ten miles an hour, including all stoppages, and think it is speed enough for any reasonable man.' And so it was, according to the means employedmeans which involved no small amount of suffering and cruelty to animals; but now that locomotive power has become a general mode for the transmission of men and chattels, the very persons who were so timid, and so dreading consequences, are now among its warmest advocates and substantial patrons. Yet this must not be regarded as an ultimatum, but merely a step in the ever-advancing course of improvement. Seeing how former inventions have been treated, on their first introduction to public notice, by the populace at large, it is no more than experience has taught us to expect, that every bold invention, developing some new power, should meet with a similar treatment; and upon this principle, a host of prejudices are arrayed against atmospheric railways. The prejudices which have existed against former inventions, and subsequently given way to approbation and admiration of the highest order, induce the writer of this paper to think, that those prejudices arose from a want of information, and a consequent misapprehension of the whole invention. This is certainly the case in reference to many who are opposed to atmospheric railways; the tion and atmospheric pressure. Mr. Valance made experiments with his system at Brighton, but does not appear to have been successful, so that his patent produced him no return, while Mr. Medhurst claimed priority of the invention. There is, however, strong reason for deciding that Mr. Valance first proposed employing the power of the atmosphere against a vacuum for railway purposes, as Mr. Medhurst did a plenum. "In 1828 Mr. Medhurst republished his pamphlet of 1810, and he then proposed to use a tube comparatively much smaller, to enclose a piston in it, and to transmit its action to the outside through a longitudinal opening; he proposed also to have stationary engines twenty miles apart, for forcing in air. Of this plan he published a drawing, talk of accidents occurring by this mode of travel-derground tunnel, also availing himself of rarefacling which must, of necessity, be more fatal than accidents by the locomotive power. No mode of travelling can pledge an entire exemption from accidents. A small piece of orange peel on our ordinary pavements may occasion the death of the man who accidentally puts his foot upon it. But this is very different from a company of men looking pale with fear, dreading that a shower of pumpkins from the moon will dash them to pieces, when they have not as yet any credible testimony that there are pumpkin gardens in the moon. With the utmost respect for the fears of the timid, and the misconceptions of the uninformed, we venture to think, that a few plain matter-of-fact statements will have a tendency to dissipate their fears, and correct their misconceptions. Correct definition is the foundation of all sound informa- showing a long box, and a pipe suspended over a tion. The terms constantly employed on this channel of water, in order to make a water joint topic are locomotive power' and atmospheric or valve. According to the assertions of some of principle or power.' Locomotive power is the his friends, he made experiments with this and mechanical force identifying itself with the car- failed, from the impossibility, explicitly says one, riages moved. Atmospheric power is a mechani- of making the continuous communication from the cal force acting on the carriages through different inside of the pipe to the carriage tight enough to media a force renewable at intervals on the line allow a useful degree of rarefaction to be pro-so that the atmospheric power is often classed duced; Mr. Pinkus, however, says that he was with the stationary, as the impulse, or cause of well informed that Mr. Medhurst never made a motion, is only at intervals, as in some railways, single experiment. The suggestion of that mode such as Blackwall, the rope by which the car- of railway transit appears to be fairly due to Mr. riages are moved is put in motion by a power that Medhurst; the important step of creating a vais entirely fixed and distinct from the carriages cuum before the piston belongs to Mr. Valance, themselves. The history of atmospheric railways while the further improvement of attaching the will satisfactorally show that the principle is not piston to an external carriage is disputed by Mr. so new-and, consequently, the plans constructed Medhurst and Mr. Pinkus; Mr. Medhurst's pamon it by no means so jejune and immature-as phlet is certainly the first publication, while Mr. some imagine. If seven cities have contended for Pinkus quotes no evidence as to his own claims. the honor of being the birthplace of Homer, it is On the 1st of March, 1834, Mr. Pinkus brought no wonder that many persons who have had think-out his first patent; and in this he proposed as a ings and imaginings on the subject, should contend valve, one in the form of a cord or rope, and for the honor of being the inventor of the atmos- which he calls a valvular cord. Mr. Pinkus pheric mode of propulsion. There are some diffi-states that in 1830 he had again prepared fresh culties in tracing this Nile to its right source; the plans and specifications, such as are now enrolled, first authentic data, however, which we have im- and that he had exhibited them to his friends, and mediately connected with the subject, is the pub-in 1833 commenced his patent. In 1834 he conlication of a pamphlet in 1810, by Mr. Medhurst, structed a large working model, which was pubin London, in which he proposed the idea of em- licly exhibited in Wigmore street; according to ploying the power of the atmosphere created in an the Samuda advocates, the experiments were a extended tube laid between the rails and commu- complete failure; but in 1836 an association was nicating the moving power thus obtained to propel formed for working under Mr. Pinkus' principle, carriages travelling along a road. Mr. Pinkus, and contracts were made for works, to demonstrate however, asserts, that Mr. Medhurst only pro- the principle. In 1836 Mr. Pinkus took out posed the impracticable part of Papin's plan of another patent for this country, with improveforcing air under the compression of many atmos-ments, and also for foreign countries; in this the pheres, as several others before him had done, valve was formed of iron plates, secured to felt, to adding, at a subsequent date, the idea of moving lay against pieces of wood, which he proposes to a piston through an under-ground tunnel, by forc-fix to the inner sides of the trough, as presenting ing in air behind it, from distances of twenty miles a smoother surface than cast-iron: he also deapart, and, by means of such piston and tunnel, impelling passengers and goods. Medhurst's first plan was to convey letters and goods by means of rarefaction and compression of air in a channel six feet high and five feet wide, contained in a paved road or iron railway. Mr. Medhurst, it should be observed, took out no patent, performed no experiments, and distributed his pamphlets chiefly amongst his friends; so great controversy has always existed as to the legitimacy and extent of his claims. In 1824 he contested his claims to invention, in a paper war with Mr. Valance; and in 1840, Mr. Pinkus contested them. In 1817, Mr. Lewis proposed a plan, which was a modification of that of Medhurst's. In 1824, Mr. Vaance took out a patent for this method of an un scribed a spring copper valve, fastened at its foot pure atmosphere of heaven as you quietly glide on by an invisible power, and entire freedom from the clanking of cumbrous machinery, flying sparks, hot cinders, and strong sulphuretted hydrogen. Another advantage is, increased speed-the average rate of travelling by the atmospheric power being fifty miles an hour, while the highest velocity of travelling on the fastest line, by steam, is thirty miles an hour; and, in a country where time is appreciated as property of great value, this must be considered of paramount importance did it exist alone; but when speed can be secured at less expense, and with increased safety and comfort, no doubt can exist to which system the most decided preference is to be given. these assertions of Mr. Pinkus we have not seen a satisfactory answer; certain it is, that on the 3rd of January, 1839, a patent was taken out by Messrs. Clegg and Samuda, from which practical results have been obtained. The grand principle of the improved atmospheric plan, up to this period, was herinetically sealing the valve with a composition each time the train passed. In 1838, experiments had been made on this plan at Chaillot, through the exertions of Mr. James Bonfit. Next, an extensive experiment was performed on Wormwood Scrubbs, on the West London Railway, Mr. Pinkus' apparatus having been removed, his company falling to the ground for want of funds. The portion of the line selected was half a mile long, with a rise of 1 in 120 for rather more than "The plans of atmospheric railways, now fairly half the distance, and 1 in 115 for the remainder. before the public, claim our particular attention. On the 11th of June, 1840, this line was opened The first we notice is that of Clegg and Samuda; for experiments, and these were attended with and we cannot do better than give the descripsufficient success, and so far sanctioned by the tion drawn up by M. Arago. We shall now say approval of eminent engineers, as to justify further a few words on the manner in which they have proceedings. We should observe, that on the 3rd contrived to establish an immediate and unyielding August, 1839, Mr. Pinkus obtained a third patent, connexion between the piston, on which the atin which he describes a valve and composition mosphere acts as a moving power, and the leadprecisely similar to Clegg and Samuda's; on the ing carriage of a train running outside the tube on 21th March, 1841, a fourth, where he proposes a the ordinary rails. This inflexible connexion, of gaso-pneumatic power. About 1841, Mr. Bonfit which we have just spoken, could not be estabset up at Havre, in the factory of M. Nilbus, lished conveniently, except by means of a metal machinery for manufacturing Clegg and Samuda's rod passing from the piston to the carriage. Now, valve. At the close of 1843, Clegg and Samuda's as it is necessary that this connexion should be plan was laid down on the Dalkey line for the short distance of one mile and a quarter; this is a continuation of the Dublin and Kingstown line. And in the subsequent history of atmospheric railways, we have last-but, as we imagine, not least the extraordinary but simple invention of Mr. James Pilbrow, which obtained a patent on the 18th November, 1844; this invention does away with the continuous valve altogether, having many other advantages which preceding inventions cannot claim. "As the two plans which now chiefly engage the attention of the public are that of Messrs. Clegg and Samuda, and that of Mr. Pilbrow, we purpose, in a subsequent part of this paper, to give a minute description of each of these plans, and a comparative estimate of both. At present we invite your attention to the general advantages of the atmospheric system above steam locomotive power. A diminution of expenditure is one of the most obvious advantages. In the original outlay there is not a necessity for that extensive levelling as is now required; engines of very great power will not be needed; the wear and tear of materials will be diminished; and, by consequence, the rates of charges for travelling will be lessened, and cheap travelling will be secured with a certainty of increased safety and comfort. This advantage of safety is one of paramount importance. The atmospheric system precludes all the terrible calamities of bursting boilers and burning trains, with which the public has become painfully familiar. Running off the line is also avoided, since, in the atmospheric system, the impelling power is at the centre of gravity, and must, from its action, keep the train on the rails. A collision of trains, from which such disastrous results have arisen, cannot possibly take place on the atmospheric principle. Then, not to enter into any metaphysical discussion of the question, how much the very consciousness of safety promotes our comfort-it may suffice to say, that the atmospheric system offers a full enjoyment of the maintained during the entire course of the piston, there must be a longitudinal opening in the upper surface of the tube. It is along this upper slit that the metal arm travels, by means of which the movement of the piston is communicated to the leading carriage of the train, and thence to all the others. This rod, or arm, has been very justly called the connecting or moving arm, or plate. But, it may be asked, if there is an opening in the tube, how is the vacuum to be produced? We give the reply. The opening is continued the whole length of a valve, by which it is hermetically closed; the vacuum can be thus successively produced in that part of the tube to the left and right of the piston, as in the closed tube, of which we have spoken in the commencement. By a movement, to which we shall presently refer, the valve is partially opened near the piston, so as to let the connecting plate pass; after which it immediately falls by its own weight. This is the most delicate part of the apparatus. If the valve actually closes the opening, a perfect vacuum is produced and maintained, by which we obtain a permanent and powerful moving force. On the contrary, should the valve allow the air to enter by any fissure, we cannot produce a sufficient vacuum but by having recourse to a very powerful air-pump-and, moreover, this imperfect vacuum can only be supported by the continual action of the pump. The longitudinal valve, which closes the opening of the tube, is formed of a strip of leather of indefinite length, strengthened above and below by a series of iron plates of about a foot long, and not leaving a space between them of more than three eighths of an inch. Weight is thus given to the valve without destroying its elasticity. The leather is closely and hermetically fastened by one of its edges to one side of the opening. The other edge remains unattached and movable; and, when the valve is closed, it merely rests on the second lip of the opening, which has been previously covered in its entire length by a composition of wax or tallow. When the valve opens, that edge | moves, the rod works on the wheels on the inside, of the leather fastened to the tube bends, and thus turns them round, and, as they turn the wheels acts as a true hinge. The valve is never raised outside, the boxes turn also. These external to a perpendicular position; its movement never wheels are then made to act upon the train, by exceeds an angle of forty-five degrees. The mere means of a rod attached to it, similar to that atfalling of the valve by its own weight does not tached to the piston within; and thus, as the pisgive it sufficient adherence to the edge of the ton moves along inside the tube, the first carriage opening, so as to prevent the entrance of air into of the train moves along also over it outside the the tube; therefore it scarcely resumes its place tube, through the medium of this double set of before it is heavily pressed by a wheel fixed at wheels and rods. In attempting to give a comthe back of the leading carriage, to which also is parative estimate of these two plans, it is right attached a cylinder filled with burning charcoal, to state that Clegg and Samuda's plan has most for the purpose of melting the composition of of the general advantages which atmospheric tallow and wax by which the valve is held down. railways have over the present locomotive prinThis is a full description of the Clegg and Samuda ciple. The great distinction, however, between atmospheric railway. Did time allow, we might the system of Messrs. Samuda and that of Mr. also notice a similar plan by M. Hallette, of Pilbrow is this-that in the former the connexion Arras. between the carriage train and the propulsion "We come now to notice the invention by Mr. piston is direct; in the latter it is indirect, a third Pilbrow, C. E., for which a patent has been taken medium being employed. Another important disout. Now this invention does not appear to be, tinction is that the Samuda system has the prolike many of its predecessors, a mere improve- pulsion tube above ground, and has insuperable ment in some mechanical detail, but seems rather difficulties in crossing roads, and in intersecting to be a new creation-a new system altogether. other lines; the Pilbrow invention, placing the It might be asked, where Clegg and Samuda's tube below the surface, gets rid of all the objecpatent differs from Pinkus', &c., or what have tions in regard to crossing and diverging lines Clegg and Samuda done? but no one will find it from the main trunk. The continuous valve of necessary to investigate far to discover the differ- the Samuda plan, must necessarily occasion much ence here no one will ask that question as to leakage, while the Pilbrow plan, dispensing with Pilbrow's. By this plan, the necessity for the the valve altogether, no leakage from that cause continuous valve running along the upper part of can possibly arise. The leakage of Samuda's the tube is entirely avoided; the connexion be- plan is equal to 5-horse power per mile, but Piltween the propulsive principle within and the brow's only 2 horse power during the whole carriages without being obtained in a manner time of working every ten miles; the Samuda entirely distinct. The propulsion tube, instead plan requires an exhausting engine at short interof being broken, or stopped at intervals of a few vals of about two miles and a half; the Pilbrow miles, extends unbroken for the whole distance. plan can be worked with only one engine at the At intervals, on the top of the propulsion tube-interval of ten miles. The Samuda plan is remarksay every thirty feet-there are placed boxes and ably complex, and, therefore, may be subject to supports. Within these boxes are cogged wheels frequent interruptions for repairs. As M. Arago or smooth-surfaced wheels, (a combination of the inquires-Can we hope for future success from two, as the model is now before you,) working a system, into which enters, as principal agents, horizontally on an axle or shaft, the upper portion a strip of leather of immense length, a composition of which passes through an aperture in the top of wax and tallow, and a hot iron to dissolve the of the box, and at the outside, or above these wax?' Now, the Pilbrow plan is remarkable boxes, the same axles are made to bear rollers or for its simplicity, and the fewness of agents emwheels similar to those inside the box. The pas-ployed. It is much to be lamented that the Pilsages through which the shafts pass are rerdered brow plan has been attacked, and difficulties asair-tight by the shoulders or flat fillet turned upon cribed to it, for which no grounds whatever exist the shafts. [The lecturer referred to diagrams.]-difficulties which have no existence whatever Attached to the propulsion piston is a long rod but in the imagination of the objector. Even the or bar, nearly fitting the small square channel or imagined difficulties must be frankly met, such tube, cast upon the propulsion tube; and, running as the fine ground metallic surfaces of the along with the piston, is conducted by this smaller wheels soon being injured; the friction and tube between the lower wheels. Either side of wear of the spindles by dust;' but the most forthis bar is covered with cogs, or is smooth, or a midable objection was stated against the use of combination of the two, as the case may be, [the cogs-that great speed would certainly break or lecturer referred to diagrams and model,] corre- strip the cogs. Now, the inventor has stated sponding with the surface of the wheels within in his pamphlet, and in this room, (January 8,) the boxes above described. It should be men- that you may dispense with the cogs, and make tioned, also, that these wheels, or rollers, are use of adhesion, or a combination of the two, at made to project in a slight degree within the high velocities, though it is right here to state, smaller tube. [The lecturer pointed out the dis- that an experiment has been made with the cogs tinction between the adhesion and cog plan; the at the rate of fifty-five miles per hour, and they latter not being indispensable, but, on the con- did not break or strip. It, however, would be trary, arrangements which many prefer.] As perfectly useless to spend time in refuting objecto the model in particular, which meets all the tions which have been either anticipated or already objections raised against other forms or arrange- proved groundless." 6 ments of this invention, the manner of working One very important point which we deem it the apparatus is simply this :-the air being ex-right to notice, is, that it is immaterial whether hausted from the propulsion tube, the piston, with cog-wheels, threaded-grooved-wheels, or plain its rod attached, is moved along inside it by the surface-wheels, be employed. The principle of pressure of the external atmosphere; and, as it the invention is the entirely new method by which |
